This invention relates to the protection of an edge of roll shaped articles such as coils of sheetmetal, plastics; pallets; and the like.
Edge-protectors are used in industry as packaging to protect the edges of many products, e.g. pallets and coiled steel and paper products.
Conventionally, edge-protectors have been made of laminated cardboard or compositions containing recycled paper and plastics materials. In their simplest configuration, they are produced as long lengths of xe2x80x98Lxe2x80x99 shaped transverse cross-section, usually rigid, and are cut to length as required. They are then attached over the edges of the product to be protected and held in place by any convenient means, e.g. staples, tape or a protective finish. Edge protectors of plastic materials can also be extruded to the desired L-shaped cross-section and then cut to lengths as required.
Where the products to be protected have substantially uniform edges, the manufacture and fitting of an L-shaped protector is a relatively straightforward operation. However, problems arise when it is desired to fit edge-protectors to non-uniform edges, e.g. coiled steel or paper products. It will be appreciated that the edges of such rolled products cannot so easily be covered by a rigid or fixed angle edge-protector as the protector must be flexible to follow the curves of the product while having the ability to conform closely to both surfaces of the product that define the edge to be protected.
It is an object of the present invention, therefore, to provide improved means (either manual or automatic) for edge-protection which is particularly suitable for use in protecting the edges of generally roll shaped articles that are non-linear.
Accordingly in one aspect the invention provides a method of protecting the edge portion of an article by means of a generally L-shaped edge protector, the protector being formed from a length of plastics sheet material having an indentation extending longitudinally along a major surface of the length and extending only partially into the thickness of the length, the indentation dividing the length into web portions, the method comprising:
locating a reel of the edge protector adjacent the article whose edge is to be protected;
unreeling an unformed (flat) length portion of the reel and advancing it towards the article;
passing the length portion through a former to bend one web portion relative to the other to form a generally L shape edge protector, and
applying the L shaped edge protector with the article along the edge.
If necessary the portion of the protector in contact with the article can then be separated from the length.
Preferably the exact angle of the bend is defined by the former.
In another aspect the invention provides an edge-protector for use in a method as defined comprising an elongate sheet of plastics material, the sheet having an indentation extending longitudinally along a major surface of the sheet and extending only partially into the thickness of the sheet, the indentation dividing the sheet into two web portions, the sheet being folded about the line of the indentation into a substantially L-shaped cross-sectional shape to provide the edge protector.
It may be preferred that the indentation or cut extends along the centre line of the sheet material so that an equal width of material is provided on each side of the cut but this is not essential. The indentation preferably extends continuously for the whole length of the sheet material.
The indentation divides the sheet into two web portions. These web portions are usually referred to as the xe2x80x98shoulderxe2x80x99 and the xe2x80x98legxe2x80x99 and for use to protect a product with a curved surface, the shoulder usually rests on the curved surface with the leg extending down the adjacent surface. Thus each web covers and protects one of the two surfaces defining the edge to be protected. We have surprisingly found that the sheet may be folded about the indentation line such that the two webs may be positioned at an angle to each other, e.g. 90xc2x0, and that they will remain in that position for a significant period of time, i.e. their recovery towards their original unfolded configuration is slow. (Although the angle between the webs is most usually about 90xc2x0, it will be appreciated that any other angle may be selected to suit the particular packaging requirements). Thus after the material has been cut to the desired length, the webs may be folded to the desired angle and then positioned over the edge to be protected and they will remain at the desired angle while the edge-protection operation is carried out and until well after the protector has been fixed in the desired position. The folding to the desired angle may be carried out manually, with mechanical resistance or fully automatically. The amount of mechanical assistance required may vary according to the depth of the indentation. It will be observed that there is no deformation on the underlying non-indented surface.
This surprising effect is not achievable by operations other than providing the indentation or cut line partially through the thickness of the sheet. Thus, for example, if significant plastic material is removed to form the line about which the edge protector is to be folded, e.g. by milling a longitudinal groove in the surface of the sheet, the effect is quite different and the folded webs cannot be maintained at the desired angle during fitting of the edge-protector without some additional restraint to prevent them returning towards the original flat configuration.
Although not wishing to be limited to any particular theory, it is believed that the advantage of the present invention in this respect is due to the deformation of the plastic material initiated by the indentation.
The plastics material is preferably polyethylene or polypropylene but any other suitable materials may be used, e.g. ethylene-propylene copolymers. Polyethylene is a particularly preferred material and although it may be of low, i.e. down to about 0.9, density or high, i.e. above about 0.95, density, it is especially preferred to use a medium density polyethylene, i.e. of density about 0.94.
The depth of the indentation required to give the desired fold and deformation properties will, of course, depend on the thickness of the sheet material, the plastics material used and the compounding ingredients used in the plastics material. Typical plastics edge protectors of the invention may be from 0.5 to 6.0 mm thick and, by way of example only, the indentation or cut may be from 10 to 60% of that thickness.
It will be appreciated that the skilled man of the art will readily be able to determine by trial and error the preferred depth to use for any particular plastics sheet material.
The edge-protectors of the present invention may conveniently, due to their flexibility, be stored and transported in reel form until such time as lengths are required to be cut from the reel for use. They are particularly advantageous for the protection of rolls, e.g. of steel or of paper, e.g. high quality photographic print paper.
In a particularly preferred embodiment, one of the two webs defined by the line of the indentation or cut is shaped or otherwise physically treated to enable it to adjust longitudinally as the edge-protector is applied to a curved edge. For example this web may be provided with diagonal cuts completely through its thickness and extending from its outer edge to the central cut line. Alternatively, this web may be formed to have a saw tooth profile, the points of the teeth being at the outer edge of the web.
In another aspect the invention provides a reel of plastics sheet material, the sheet having an indentation extending longitudinally along a major surface of the sheet and extending only partially into the thickness of the sheet, the indentation dividing the sheet into two web portions, a length of the sheet when pulled off the reel being foldable about the line of the indentation to form an edge-protector of substantially L-shaped cross section.
Where the protectors of the invention are made in configurations such as the saw-tooth arrangement discussed above, they may conveniently be made, e.g. extruded, in multi-width form and then cut longitudinally to provide lengths of separate edge-protectors. In this embodiment the sheet material may be passed beneath multiple tools to impart the cut lines in the parts of the width simultaneously or the indentation or cut line may be introduced after separation into single lengths.
The products of the invention have been found to be eminently suitable for automatic application to coiled materials by continuous automatic methods.